N-(PEG3-acid)-N-bis(PEG3-amine)

This PEG-based linker is designed for constructing PROTACs that require flexible, hydrophilic spacers to connect a ligand-bearing warhead to an E3-recruiting moiety. Its poly(ethylene glycol) architecture supports improved solubility and can help tune effective intramolecular geometry and linker accessibility in targeted protein degradation workflows. The detailed structural and synthetic considerations are provided below for researchers planning PROTAC assembly and subsequent conjugation steps.

Structure: N-(PEG3-acid)-N-bis(PEG3-amine) contains a central carboxylic acid functionality and multiple terminal PEG ether segments bearing amine groups. The molecule features ether linkages within the PEG chains, an amide-forming carboxyl group, and primary amines suitable for coupling. Overall, it is highly polar and water-compatible.

Reactivity: The carboxylic acid can be activated for amide-bond formation using standard coupling chemistries (for example, carbodiimide-based activation with an appropriate additive) in polar aprotic solvents. The primary amines enable nucleophilic substitution or amide coupling after activation of the complementary partner (such as an activated ester or carboxylate). In PROTAC synthesis, sequential coupling strategies are commonly employed to preserve functional group integrity and maintain linker flexibility; inert atmosphere and controlled pH are often used to minimize side reactions.